1. Field of the Invention
The present invention relates to a multitubular catalytic gas-phase reaction apparatus suitable for use in the production of chlorine gas.
2. Description of the Related Art
Conventionally, production of industrial gases such as chlorine gas and acrolein that are generated by catalytic gas-phase reaction, generally uses a multitubular reaction apparatus for effective removal of heat generated by exothermal reaction. A multitubular reaction apparatus includes a plurality of reaction tubes charged with a catalyst within a reactor shell, and circulates a heat exchange medium (heat medium) within the reactor shell to cool the reaction tubes and thereby removes reaction heat.
In exothermal reaction using a multitubular reaction apparatus, so-called hot spots may be generated in sites where the efficiency of removal of reaction heat is worsened by drifts of a heat medium flow, or in sites where the catalyst concentration is high and so the reaction speed is high, or the like. In the hot spots, deterioration of a catalyst or a decrease in purity of a reaction product is prone to readily occur due to extreme temperature rises.
When a heat medium is supplied to remove heat of a reactor, the flow of the heat medium in the horizontal direction (lateral direction), that is, in a direction perpendicular to the longitudinal direction of the reaction tube, primarily controls the efficiency of heat removal of the reactor. Accordingly, in order to restrain generation of hot spots, it is effective to control the flow of a heat medium within a reactor shell being homogenized in the lateral direction.
As a method of restraining the generation of hot spots, U.S. Pat. No. 3,871,445 discloses a reaction apparatus including a multitubular reaction tube equipped with a circulation device of a heat medium and a reactor shell having baffles arranged therein. It describes that the presence of the baffles maintains the substantially constant rate of the lateral flow of the heat medium, i.e., the flow in the direction perpendicular to the longitudinal direction of the reaction tubes, within one compartment separated by the baffles. However, in the method described in U.S. Pat. No. 3,871,445, heat removal in the vertical flow, i.e., in the flow in the direction along the reaction tubes is poor as compared with heat removal in the lateral flow, so the heat transfer within one compartment is not sufficiently constant.
On the other hand, European Unexamined Patent Publication No. 10B0780 discloses that, in a multitubular reactor having a disc baffle, the disposition of a space having no reaction tubes arranged therein in the central portion of the reactor shell reduces the influence of a decrease in heat removability due to a vertical flow. However, in this case also, in a site where a heat medium flow in the end portion of the baffle is reversed, portions poor in heat removability in some reaction tubes remain, causing the generation of hot spots in some cases.
European Unexamined Patent Publication No. 1466883 discloses that, in a gas-phase catalytic oxidation method by means of a fixed bed multitubular heat exchange reactor, for the purpose of prevention of hot spot generation arising from nonuniformity of a heat medium flow within a reactor shell, the reaction conditions within the reaction tubes are estimated and the way of charging a catalyst in the reaction tubes is changed on the basis of the results of the estimations in such a way that the nonuniformity of reaction conditions among the reaction tubes is reduced. This case, however, poses a problem in that the method of charging a catalyst is too complicated.